In radiology, stringent demands are made or imposed on the quality of images. For radiology images made for radiological medical diagnosis for example, X-radiation from a virtually punctate X-ray source is passed through an object to be examined, and a distribution of an attenuation of the X-radiation is detected two-dimensionally on a side of the object diametrically opposite the X-ray source. In computed tomography, line-by-line detection of the X-radiation attenuated by the object is made. Solid-state detectors are increasingly used as radiation detectors. These solid-state detectors have a matrix like array of semiconductor elements that act or operate as receivers. The X-ray image or projection achieved or made is composed of a plurality of individual pixels, and ideally, the attenuation of the radiation through the object along a straight axis or path from the X-ray source to a location on the detector surface corresponds to each of the plurality of pixels. The radiation that strikes the detector along this straight axis is referred to as a primary radiation.
However, during the passage of the X radiation through the object, interactions necessarily occur between the X-ray beams and the object, which leads to scattering effects. That is, besides the primary beams, which pass un-scattered through the object, secondary beams also occur, which strike the detector having deviated from their respective rectilinear axis or path. These secondary beams, which can make up a substantially high proportion of an entire signal modulation of the detector, are an additional source of noise and reduce a capability of detecting finely contrasting image distinctions.
For reducing the scattered radiation striking the detector, it is known to employ scattered radiation grids. Known scattered radiation grids comprise regularly arranged structures which absorb X-radiation, and between which through conduits (channels or ducts), or the like, for primary radiation are provided. A distinction is made between focused grids and unfocused grids. In focused grids, the through conduits and thus the absorption structures that determine them are aligned with the focus of the X-ray source, in contrast to unfocused grids, in which the conduits are perpendicular to the detector surface.
A mode of operation of a scattered radiation grid is such that primarily the secondary radiation, and in unfocused grids also part of the primary radiation, are absorbed via the absorbing structures, and thus do not strike the detector and do not contribute to the proportion of radiation that generates the X-ray image. On one hand, the scattered beams should be maximally absorbed, yet on the other hand, a maximal proportion of primary radiation should pass un-attenuated through the grid. Reducing the proportion of scattered radiation can be achieved via a substantially high shaft ratio of the conduits. This high ratio is between a height of the grid and a thickness or diameter of the through conduits. However, due to the thickness of the absorbing elements located between the conduits, image distortion can occur from absorption of part of the primary radiation. When the grid is used in conjunction with a matrix detector, a discontinuity in the grid causes image distortion because of the projection of the grid in the X-ray image. A potential risk is that the projection of the detector element structures and the scattered radiation grid may interfere with one another, which may lead to an occurrence of interfering moiré effects.
The above discussed grid problems or issues were also described in German Patent Application DE 102 41 424.6, which was published after the priority date of the present application. In this German patent application document, a novel type of grid is described in comparison with the conventional lead lamination grids. Conventional lead lamination grids are referred to as “placed grids.” Thin lead laminations and elements, which are usually made of radio-transparent paper to form the through slits between the laminations, are placed alternatingly. However, these placed grids are limited in terms of production and manufacture and may lead to problems, such as in solid-state detectors. The grid of DE 102 41 426 is different, since being produced via a rapid prototyping technique or method using a layer-wise solidification of a buildup material. With this technique, substantially fine and exact structures can be built up, which are used for the configuration of the absorption structure. The absorption structure thus manufactured is then coated, both on the inside faces of the through conduits provided in the structure and on the diametrically opposite surfaces, with a substantially high absorbent material, and the surface coating is either reduced substantially or removed entirely in a post-treatment step or act. Although with this grid, the detectability of grid projections can be reduced and shifted into a substantially high location frequency range so that they cannot be sharply projected by the imaging systems. These grids may be expensive to manufacture, and may make stringent technical demands in terms of the course or process of manufacture. This is applicable when removing the coating from the face ends of the structure produced by stereo-lithography, which during the removal process itself may not be affected. However, a homogeneous reduction in the layer thickness or a substantially homogeneously complete removal may be necessary, so that a locally varying absorption behavior may not occur. Moreover, the coating of the insides of the through conduits needs to be or remain unaffected.
Similar problems to those in radiological diagnosis also occur in nuclear medicine, when gamma scanners or cameras are used for example. There again, care is taken such that a minimal amount of scattered gamma quanta may reach the detector. In this type of examination, the X-ray source for the gamma quanta is located in the interior of the object being examined. After an unstable nuclide has been injected, an image of an organ is generated by the detection of the quanta emitted from the body because of the decomposition of the nuclide. The course of the activity or decomposition in the organ over time allows conclusions to be drawn about a function of that organ. In this technique, as in a scattered radiation grid, a collimator is placed in front of the gamma detector and the collimator determines the projection direction of the image. In operation and construction, this collimator may be similar to the scattered radiation grid described at the outset.